We present the results of radio observations of red supergiants in a star cluster, Stephenson (1990AJ.....99.1867S)'s #2 (Cl Stephenson 2), and of candidates for red supergiants in three star clusters, Mercer et al. (2005ApJ...635..560M)'s #4, #8, and #13 ([MCM2005b] 4, [MCM2005b] 8 and [MCM2005b] 13), in the SiO and H_2_O maser lines. The Stephenson's #2 cluster and nearby aggregation at the southwest contain more than 15 red supergiants.
SiO and H2O maser survey toward AGB & post-AGB stars
Short Name:
J/ApJS/211/15
Date:
21 Oct 2021
Publisher:
CDS
Description:
Simultaneous observations of SiO(v=1,2,J=1-0) ^29^SiO(v=0,J=1-0) (43.122080GHz, 42.820587GHz and 42.879916GHz) and H_2_O(6_16_-5_23_) (22.235080GHz) maser lines were performed with three KVN (Korean VLBI Network) 21m single-dish radio telescopes (at Yonsei University campus, Ulsan University campus, and Tamna University campus) toward the 164 post-AGB and 143 AGB stars. Observations were carried out from 2011 February to 2012 March.
We present simultaneous observations of several rotational lines of ^28^SiO in the v=1, 2, 3, and 4 vibrationally excited states toward O-rich evolved stars. All the data were taken in a relatively short period of 65 days, which allows a comparative study of the ^28^SiO maser lines intensities and profiles. The observed differences concerning intensity and line shape among the different maser lines suggest that infrared overlaps deeply affect the pumping of some SiO masers. We qualitatively discuss this effect with consideration to the IR overlaps at 8 {mu}m between the various SiO isotopomers and between ^28^SiO and water vapor
We aim to study the time evolution of the SiO maser lines in Mira-type and semi-regular variables at short timescales. We observed the SiO maser lines at 7mm and 3mm using the 40m Yebes antenna and the 30m IRAM telescope, respectively, with a minimum spacing of 1 day. We studied the semi-regular variables RX Boo and RT Vir and the Mira-type variables U Her, R LMi, R Leo, and chi Cyg.
We searched for the SiO J=1-0, v=1 and 2 maser lines at ~43GHz in 277 2MASS/MSX/IRAS sources off the Galactic plane (|b|>~3{deg}), which resulted in 119 (112 new) detections. Among the new detections, two are very faint objects with MSX 12{mu}m flux densities below 2Jy. These are likely to be O-rich AGB-stars associated with dwarf-galaxy tidal tails. The sample also includes medium bright MSX objects at moderately high galactic latitudes (3{deg}<|b|<5{deg}) and in the IRAS gap at higher latitudes. A signature of a warp of the inner Galactic disk is found for a disk subsample. This warp appears relatively strongly in the area of 0{deg}<l<45{deg} and 3{deg}<|b|<5{deg}. We also found a group of stars that does not follow to the Galactic rotation. This feature appears in the Galactic disk at l~27{deg}, and extends more than 15{deg} in the galactic latitude, like a stream of tidal debris from a dwarf galaxy.
We present a search for SiO masers towards a sample of 126 objects including OH/IR stars, proto-planetary and planetary nebulae. All objects are classified as oxygen-rich, and most of them are associated with OH or H_2_O masers. SiO masers were found only in variable objects like the OH/IR stars and a few objects classified as proto-planetary nebulae, but with variable central stars that may be part of binary systems. In one object, OH 15.7+0.8, which appears to be varying irregularly and most likely recently left the AGB, an SiO maser was tentatively detected. Thus, we conclude that variability and SiO maser emission are closely linked, and that SiO masers disappear very soon after a star has reached the end of the AGB, when pulsation and mass loss cease.
The observations in the 28SiO J=1-0 v=1, J=1-0 v=2 lines and the 29SiO J=1-0, v=0 lines were simultaneously made toward 181 color-selected IRAS sources in the outer disk of the Galaxy (at longitudes between 90 deg and 250 deg). The 28SiO lines were detected in 63 sources (56 new) and the 29SiO line in 11 sources (9 new). Most of the detections are optically variable stars, mainly Mira-type variables and a few semiregular variables. The detection rate (35%) is much lower than that of the bulge survey performed by the same observational system - the 45m telescope at Nobeyama Radio Observatory. The lower detection rate of SiO maser emission is partly attributed to the increase of contaminations by stars with C-rich circumstellar envelopes and young stellar objects in the outer disk sample. The kinematical implications of the observational results are also discussed. The luminosity distances to the SiO maser sources are estimated from their IRAS fluxes at 12um and colors. By combining the SiO radial velocity and the luminosity distance, the rotation curve of the outer Galactic disk is found to be slightly falling within the Galactocentric distance between 8.5 and 12kpc. The sources located within 20deg from the Galactic anticenter direction are used to check for a peculiar motion of the local standard of rest.
We surveyed 291 MSX/2MASS infrared objects in the 7{deg}x2{deg} area of the galactic center in the 43GHz SiO J=1-0 v=1 and 2 maser lines, obtaining accurate radial velocities of 163 detected objects. The surveyed area is the region where the IRAS catalog is incomplete due to contamination by high source density. The objects in the present MSX/2MASS sample were chosen to have similar infrared characteristics to those of the previous SiO-maser-survey samples based on the color-selected IRAS sources. The sampling based on the 2MASS catalog causes a bias to the foreside objects of the bulge due to heavy obscuration by interstellar dust; the detections considerably leaned on the V_lsr_<0 side.
We have surveyed ~400 known large-amplitude variables within 15' of the galactic center in the SiO J=1-0 v=1 and 2 maser lines at 43GHz, resulting in 180 detections. SiO lines were detected from 16 other sources located within 20" of the program objects. The detection rate of 48% is comparable to that in bulge IRAS surveys.
We present the results of observations of cold IRAS sources in the Galactic disk area, -10{deg}<l<100{deg} and |b|<5{deg}, in the SiO J=1-0, v=1 and 2 maser lines. SiO masers were detected in 51 out of 143 observed sources; 45 were new detections in SiO masers. The selected IRAS sources were objects with dust temperatures of between 160 and 280K.
